Method of lining branch pipe portion of underground main pipe with rigid plastics tube

ABSTRACT

A method of forming a rigid or semirigid plastics tube lining over the inner surface of a branch pipe portion as joined at its one end to an underground main pipe through the other end thereof substantially open to the surface of the ground as a work opening, the method being characterized by inserting a rigid or semirigid plastics tube into the branch pipe portion from the work opening with the forward end of the tube substantially closed, and subsequently supplying a fluid into the tube to inflate the tube radially of the branch pipe by applying heat and pressure to the tube with the fluid from inside directly or indirectly and thereby line the branch pipe portion with the rigid plastics tube. The pipe portion can be lined from the ground surface efficiently without necessitating labor for excavation of the ground, cutting off the branch pipe portion and restoring the piping to the original state.

TECHNICAL FIELD

The present invention relates to a method of lining branch pipe portionsof underground main pipes with a rigid plastics tube, and moreparticularly to a method of forming a rigid plastics tube lining overthe inner surface of the branch pipe portion as connected at its one endto the underground main pipe through the opening at the other endthereof, i.e., from the surface of the ground.

BACKGROUND ART

A method of lining pipes is already known wherein a rigid plastics tubeinserted in the pipe and having a smaller diameter than the pipe isinflated radially of the pipe by applying heat and pressure to the tubefrom inside and thereby line the pipe with the rigid plastics tube (see,for example, Unexamined Japanese Pat. Publication No. 88281/1983).

The rigid plastics tube lining is hard, therefore retains itself in thepipe lining state and is more excellent in quality than the soft tubelining which is bonded with an adhesive to the pipe for lining.

No particular problem is experienced in using the rigid plastics tubelining method for lining underground main pipes such as water supplypipes, gas pipes and sewer pipes, whereas a problem arises when a branchpipe portion extending from the main pipe to the surface of the groundis to be lined by this method. Since the branch pipe portion has one endconnected to the main pipe, it is very difficult to carry out liningwork through the opening of the other end which only is usable as a workopening.

In this case, the problem can be eliminated by excavating the ground andcutting off the branch pipe portion from the main pipe to form anotherwork opening and line the pipe portion through both ends as in the usualwork condition. However, this requires much labor and time forexcavating the ground, cutting off the branch pipe portion and restoringthe piping to the original state, hence an undesirable solution.

DISCLOSURE OF THE INVENTION

The main object of the present invention is to provide a method oflining a branch pipe portion of an underground main pipe with a rigidplastics tube easily and reliably through one end of the branch pipeportion from the surface of the ground.

Other features of the invention will become apparent from the followingdescription.

The present invention provides a method of forming a rigid or semirigidplastics tube lining over the inner surface of a branch pipe portion asjoined at its one end to an underground main pipe through the other endthereof substantially open to the surface of the ground as a workopening, the method being characterized by inserting a rigid orsemirigid plastics tube into the branch pipe portion from the workopening with the forward end of the tube substantially closed until theclosed end is brought into the main pipe, subsequently supplying a fluidinto the tube to inflate the tube radially of the branch pipe byapplying heat and pressure to the tube with the fluid from inside andthereby line the branch pipe portion with the rigid plastics tube, andcutting off and removing an unnecessary end portion of the lining insidethe main pipe by a cutting device movable through the main pipe byremote control (hereinafter referred to as the "first method").

The invention further provides a method of forming a rigid or semirigidplastics tube lining over the inner surface of a branch pipe portion asjoined at its one end to an underground main pipe through the other endthereof substantially open to the surface of the ground as a workopening, the method being characterized by inserting a rigid orsemirigid plastics tube into the branch pipe portion from the workopening with the forward end of the tube left open until the forward endreaches an opening at said one end of the branch pipe portion,subsequently applying heat and pressure to the rigid plastics tube witha fluid from inside through a collapsibly inflatable soft tube freelyinserted in the rigid plastics tube over the entire length thereof toinflate the rigid plastics tube radially of the branch pipe and therebyline the branch pipe portion with the rigid plastics tube, andthereafter withdrawing the soft tube from inside the lining (hereinafterreferred to as the "second method").

The methods of the present invention are used for lining branch pipeportions branching toward the surface of the ground from undergroundmain pipes such as water supply main pipes, gas main pipes and sewermain pipes.

The methods of the invention are practiced for the branch pipe portionas joined at its one end to the underground main pipe through the branchpipe other end which is substantially open to the surface of the groundas a work opening.

When the main pipe is a water main or gas main, the branch pipe otherend is removed at the portion where a meter is mounted for the user sothat the branch pipe portion is opened to the surface of the ground.When the main pipe is a sewer, the branch pipe other end is joined to agully in a gutter formed in the ground surface and left open to theground surface at the junction. The branch pipe other end thus open tothe ground surface is utilized as a work opening.

The rigid or semirigid plastics tube to be used for lining by themethods of the invention must be thermoplastic so as to be inflatable bythe heat and pressure applied thereto by a fluid from inside. The rigidplastics tube is usually made of polyvinyl chloride, polyethylene,polypropylene or like material which is 60° to 100° C., preferably about70° to about 95° C., in softening point.

The rigid plastics tube made of the above material is circular in crosssection and has an outside diameter smaller than the inside diameter ofthe branch pipe portion, for example, an outside diameter correspondingto about 50 to about 90% of the inside diameter.

The rigid plastics tube has such a wall thickness that the resultinglining is capable of retaining its shape and strength for use as suchwithout application of any adhesive. Usually, the thickness is in therange of about 1 to about 10 mm and is determined according to theinflation ratio, outside diameter, material, etc.

The rigid or semirigid plastics tube is used as shaped to a circularcross section or as collapsed radially to the form of a belt. The tubeis collapsed to the belt form preferably as softened by heating. Therigid plastics tube thus deformed is flexible owing to its belt form andinherent elasticity and insertable through a bent branch pipe portionfree of trouble. If the rigid plastics tube in the form of a belt islikely to buckle when passing through the bend, the tube can beprevented from buckling by being reinforced with a linear spring memberinserted therethrough before use.

The fluid to be used for applying heat and pressure to the rigidplastics tube from inside is not limited specifically but is preferablysteam which has a great heat capacity, becomes water on condensation andis dischargeable as it is without entailing any pollution.

The fluid has a temperature higher than the softening point of the rigidplastics tube and a pressure which overcomes the tensile strength of therigid plastics tube as softened by heating.

With the first method of the invention, the rigid plastics tube isinserted, with its forward end closed with a front plug, into the branchpipe portion through the other end thereof serving as a work opening.When the rigid plastics tube is continuously inserted, the forward endof the rigid plastics tube passes through the branch pipe end joined tothe main pipe, strikes against the wall of the main pipe inside thereofand becomes no longer insertable, so that the rigid plastics tube can beinserted through the branch pipe portion over the entire length thereofwithout the necessity of measuring the length of the branch pipeportion. The rigid plastics tube may be inserted into the branch pipeportion while being heated with steam or like fluid from inside.

After the rigid plastics tube has been inserted through the branch pipeportion, the heating and pressurizing fluid is supplied to the inside ofthe tube to inflate the tube radially thereof with heat and pressure,whereby the branch pipe portion can be lined with the rigid plasticstube.

After the rigid plastics tube lining has been formed, the forward endportion of the lining remains inside the main pipe. The unnecessary endportion of the lining is cut off and removed by a cutting device whichis movable through the main pipe by remote control. Such a cuttingdevice can be obtained, for example, by mounting on a work machinemovable through the main pipe by remote control a hollow cylindricalcutter having a saw-toothed forward end and drive means for rotating thecutter about its center axis.

The first method of the present invention is adapted to line a branchpipe portion with a rigid plastics tube through the other end opening ofthe pipe portion as a work opening, i.e. from the surface of the ground.Accordingly, the method requires little or no restoring work afterlining, consequently achieving savings in labor and time for a costreduction.

The second method of the invention is substantially the same as thefirst method but differs therefrom in the following features.

(a) The rigid plastics tube is inserted into the branch pipe portion toposition the forward end of the rigid plastics tube in coincidence withone end (joined to the main pipe) of the branch pipe portion withoutprojecting the tube end into the main pipe.

(b) Heat and pressure are applied indirectly to the rigid plastics tubeinserted in the branch pipe portion through a soft tube inserted throughthe rigid plastics tube to inflate the rigid plastics tube and line thebranch pipe portion with the rigid plastics tube.

According to the second method, the rigid plastics tube does not projectinto the main pipe, so that no unnecessary end portion of the rigidplastics tube lining remains within the main pipe. Thus, the secondmethod is superior to the first method in that the unnecessary endportion need not be cut off and removed from inside the main pipe.

With the second method, the soft tube to be used for inflating the rigidplastics tube is made, for example, of heat- and pressure-resistantrubber, free to inflate and collapse and recovered by being drawn outfrom the rigid plastics tube lining to above the ground after the liningoperation.

Before practicing the second method, it is necessary to measure thelength of the branch pipe portion to position the forward end of therigid plastics tube in coincidence with the above-mentioned one end ofthe branch pipe portion. The length can be measured, for example, bymeasuring the overall length of the branch pipe portion inclusive of thediameter of the main pipe with a piano wire inserted through the branchpipe portion through the other end thereof and subtracting the diameterof the main pipe from the measurement.

BEST MODE OF PRACTICING THE INVENTION

Embodiments of the invention will be described below with reference tothe accompanying drawings, in which:

FIG. 1 is a view in vertical section schematically showing the step ofinserting a rigid plastics tube into a branch pipe portion in the firstmethod of the invention;

FIG. 2 is a view in section taken along the line I--I in FIG. 1;

FIG. 3 is a view in vertical section schematically showing the rigidplastics tube as completely inserted;

FIG. 4 is a view in vertical section schematically showing the step ofinflating the rigid plastics tube;

FIG. 5 is a view in section taken along the line II--II in FIG. 4;

FIG. 6 is an enlarged fragmentary view in section schematically showinghow to cut off an unnecessary end portion of the rigid plastics tubeinside a main pipe;

FIG. 7 is a view in vertical section schematically showing amodification of the first method;

FIG. 8 is a fragmentary sectional view showing the same on completion oflining operation;

FIG. 9 is a view in vertical section schematically showing the step ofinserting a rigid plastics tube into a branch pipe portion in the secondmethod;

FIG. 10 is a view in section taken along the line III--III in FIG. 9;

FIG. 11 is a view in vertical section schematically showing the step ofinflating the rigid plastics tube;

FIG. 12 is a view in vertical section schematically showing a rigidplastics tube lining formed; and

FIG. 13 is a view in section taken along the line IV--IV in FIG. 12.

FIGS. 1 to 8 show a mode of lining a branch pipe portion c of anunderground sewer main pipe a with a rigid plastics tube 1 by the firstmethod of the invention. The branch pipe portion c has one end joined tothe sewer main pipe a and the other end to a gully b in a gutter formedin the surface of the ground.

The rigid plastics tube 1 used for the present embodiment is made ofpolyvinyl chloride resin and circular in cross section. Being circularin cross section, the rigid plastics tube 1 is capable of retaining thecircular cross section with good stability reliably also afterinflation.

Based on the circular cross section, the tube 1 has an outside diameterapproximately equal to or smaller than the inside diameter of the branchpipe portion c but not smaller than about 50% of the inside diameter. Inview of the insertability into the branch pipe portion c, the tube 1 isusually deformed to an approximately U-shaped cross section as seen inFIG. 2 by being collapsed radially thereof. The tube 1 thus deformed tothe U-shaped cross section has a decreased outside diameter, is madeinsertable into the branch pipe portion c more smoothly and is flexibleowing to the inherent elasticity of the synthetic resin. Accordingly,the tube is insertable into the branch pipe portion c free of troubleregardless of whether the pipe portion is straight or bent. The tube 1is pressed for deformation usually as softened by heating.

Before the insertion into the branch pipe portion c, a front plug 2 isfitted to the front end of the tube 1 of decreased outside diameter. Theplug 2 has bores 2a extending therethrough longitudinally of the tube 1.

A linear spring member 3 is inserted through the tube 1 over the entirelength thereof. The spring member 3 reinforces the tube 1 from inside,prevents the tube 1 from bending greatly and effectively delivers apushing force to the front end of the tube. The spring member 3 may bedispensed with when the branch pipe portion c is straight. FIG. 2 showsa steel strip which is especially desirable as the linear spring member3 for backing up the tube 1 from inside over a large width.

FIG. 1 shows the step of inserting the rigid plastics tube 1 into thebranch pipe portion c. The tube 1 is inserted by being pushed from abovethe ground through the outer end opening c1 of the branch pipe portionc. The tube 1 is so pushed manually or by suitable mechanical means.

With reference to FIG. 3, the rigid plastics tube 1 inserted into thebranch pipe portion c passes through the inner end opening c2 of thepipe portion c and reaches the wall a1, opposite to the opening c2, ofthe main pipe a. The spring member 3 is then withdrawn from the tube 1to complete the insertion of the tube 1 through the branch pipe portionc.

After the rigid plastics tube 1 has been completely inserted through thebranch pipe portion c, a rear plug 4 is fitted to the rear end of thetube 1 as seen in FIG. 4, and the heating fluid, e.g. steam, is suppliedto the interior of the tube 1 through a supply hole 4a. The steamsupplied from the rear end of tube 9 flows through the tube 9 toward thefront end thereof and is discharged from the bores 2a of the plug 2while heat and pressure are applied to the tube 1 from inside, inflatingthe tube 1 radially of the branch pipe to cause the tube to cover theinner surface of the branch pipe portion c. After the tube 1 is inflatedto completely cover the inner surface of the pipe portion c, the steamis replaced by outside air with the tube 1 as held internallypressurized to solidify the inflated tube 1' by cooling. Aftersolidification of the tube 1', the pressure applied by the outside airis released from the tube 1'.

As shown in detail in FIG. 6, the tube 1 lining the pipe portion c has afront end portion 1a projecting into the main pipe a, so that theprojecting end portion 1a, which is unnecessary, is cut off and removedby a cutting device 5 which is movable through the main pipe a by remotecontrol, whereby the entire work is completed. The end portion is cutoff and removed from the main pipe a utilizing as work openings manholesnot shown) which are provided at a suitable spacing along the main pipea.

The cutting device 5 is one which is capable of cutting off and removingthe tube end portion 1a inside the main pipe a by remote control, forexample, one having a cylindrical rotary cutter 5a at the front end withrespect to the direction of advance of the device.

The lining thus obtained is formed by the rigid plastics tube 1 and istherefore capable of fully withstanding the underground water pressurepenetrating through the joints (not shown) or the like of the branchpipe portion from outside.

When the main pipe a has a tube lining d as seen in FIGS. 7 and 8, it isdesirable to seal the junction 6 between an opening portion d1 foropening the branch pipe portion c and the branch pipe portion tubelining 1' fitted in the opening portion d1. The junction 6 can be sealedby fitting a rubberlike elastic tubular member 7, uncoated or coatedwith an adhesive (not shown) on its outer periphery, around the desiredposition of the rigid plastics tube 1 to be made into the tube lining 1'on the branch pipe portion c, and pressing the tubular member 7 againstthe opening portion d1 of the tube lining d on the main pipe a at thejunction 6 when inflating the rigid plastics tube 1. The tubular member7 may be of the hotmelt type. If the steam supplied to the tube 1 isinjected into the main pipe a through the bore 2a in the front plug 2 inthis case as in the above embodiment, the tube lining d on the main pipeis liable to become unlevel by being locally softened by heating, sothat it is desirable to discharge to above the ground the steam suppliedto the tube, via a bore 2a1 of the return type formed in the front plug2 and a discharge tube 8 communicating with the outlet of the bore.

With the method of the invention, the outer end of the branch pipeportion c joined to the gully b in the gutter is utilized as a workopening for lining the pipe portion c, so that the lining operation canbe carried out with an improved efficiency without necessitating acumbersome procedure such as excavation of the ground. Furthermore, thelining, which is formed by a rigid plastics tube, fully withstands theunderground water pressure without application of adhesive, thuscovering the pipe portion for a prolonged period of time stably andreliably.

FIGS. 9 to 13 show a mode of practicing the second method of theinvention.

The rigid plastics tube 1 to be used in the present embodiment iscircular in cross section and has an outside diameter corresponding toabout 75% of the inside diameter of the branch pipe portion c to belined. The tube 1 is used as shaped to the circular cross sectionwithout collapsing.

Before the tube 1 is inserted into the pipe portion c, a collapsiblyinflatable heat-resistant tube 9 is inserted through the rigid plasticstube 1 over the entire length thereof.

The forward end of the tube 9 is projected outward beyond the rigidplastics tube 1, and the end of the projection 9a is closed with a frontplug 10. The outside diameter of the front plug 10 is smaller than theinside diameter of the rigid plastics tube 1 as inflated to form alining. A heat-resistant hose 11 is inserted through the tube 9 and hasa forward end secured to the inner end of the front plug 10 and theother end extending outward from the tube 9. The hose 11 is provided atits forward end with a metal member 12 having a communication opening12a for holding the interior of the tube 9 in communication with theinterior of the hose 11.

To line the branch pipe portion c with the rigid plastics tube, therigid plastics tube 1 having the heat-resistant tube 9 insertedtherethrough is inserted into the pipe portion c through a work opening,i.e., an opening at its outer end joined to the gully b in the gutter.When the inserted end of the rigid plastics tube 1 is positioned incoincidence with the open inner end of the branch pipe portion c, theinsertion is discontinued. The inserted forward end of the rigidplastics tube 1 can be positioned in coincidence with the inner end ofthe branch pipe portion c by inserting the tube 1 by a lengthcorresponding to the length of the pipe portion c which is measured inadvance. Alternatively, this can be accomplished by making the length ofthe projection 9a of the heat-resistant tube 9 equal to the diameter ofthe main pipe a.

When the branch pipe portion c has a bent portion, the rigid plasticstube 1 is inserted as softened by being internally heated with steam orthe like. Since the rigid plastics tube 1 is liable to collapse when notbacked up from inside, the rigid plastics tube 1 is inserted into thebranch pipe portion c preferably while being supported from inside bythe heat-resistant tube 9 inserted through the tube 1 by inflating thetube 9 to such an extent as will not inflate the rigid plastics tube 1.When desired, the steel strip 3 shown in FIG. 2 may be used incombination with the inflated tube 9.

After the rigid plastics tube 1 has been inserted into the branch pipeportion c along with the heat-resistant tube 9, the tube 9 is closed atthe rear end with a rear stopper 13 as seen in FIG. 11. The rear end ofthe rubber hose 11 is withdrawn from the pipe portion c and the tube 9through the rear stopper 13, and a shutoff valve 14 is attached to thewithdrawn end 11a.

When steam is supplied from a boiler (not shown) to the interior of theheat-resistant tube 9 through a conduit 15 and then through a supplyopening 13a in the rear stopper 13 in the state shown in FIG. 11, thesteam flows through the tube 9 from its rear end toward the front endthereof while heating the outside rigid plastics tube 1 through the tube9 and is discharged via the communication opening 12a of the metalmember 12 and then via the rubber hose 11. Instead of passing the steamthrough the rubber hose 11, the steam may be discharged through anoutlet (not shown) formed in the front plug 10.

After the rigid plastics tube 1 is heated and softened by the steam, theopening of the valve 14 is adjusted to increase the steam pressurewithin the tube 9, causing the steam to inflate the tube 9 and thereforethe outside rigid plastics tube 1 radially of the pipe portion to linethe branch portion c with the tube 1.

After the branch pipe portion c has been lined with the rigid plasticstube 1, the steam is replaced by outside air with the internal pressuremaintained in the tube 9, whereupon the rigid plastics tube 1 is cooledand solidified with the outside air. Subsequently, the pressure isreleased from the tube 9 to contract the tube 9 to recover the tube 9from inside the rigid plastics tube 1, whereby the entire liningoperation is completed.

FIGS. 12 and 13 show the branch pipe portion c formed with a rigidplastics tube lining 1' over its inner surface. The tube lining 1' isrigid, retains its shape and accordingly thereafter holds the pipeportion covered therewith stably and reliably.

With the second method, the unnecessary end portion formed inside themain pipe a by the first method need not be cut off. Thus, the secondmethod has the feature of being greatly improved in lining efficiency.

What is claimed is:
 1. A method of forming a plastic tube lining over aninner surface of a branch pipe connected to an underground main pipe atone end thereof with the other end open to the surface of the ground,the method comprising the steps of:preparing a rigid plastic tube to beused as a liner, the rigid plastic tube having a discharge meanscomprising a front plug at a distal end thereof for discharging a fluidtherethrough; inserting the rigid plastic tube equipped with thedischarge means through said other end until at least the dischargemeans extends into the underground main pipe; feeding a heated andpressurized fluid continuously into the rigid plastic tube in order toradially expand the rigid plastic tube until the rigid plastic tubecontacts the inside of the branch pipe while discharging the used fluidout of the rigid plastic tube through the discharge means; and cuttingoff a part of the rigid plastic tube within the underground main pipe;wherein the front plug at said distal end of said rigid plastic tube hasan elongated discharge pipe connected thereto and extending along thebranch pipe from said front plug to said other end of said branch pipe.2. The method of claim 1, wherein the rigid plastic tube is previouslyradially collapsed.
 3. The method of claim 1, wherein the rigid plastictube is provided with a seal member at a distal end thereof in order toprovide a seal at a junction between the branch pipe and the undergroundpipe.
 4. The method of claim 1, wherein the fluid is steam.